A 12,500 kg railroad freight car travels on a level track at a speed of 5.2 m/s. It collides and couples with a 22,600 kg second
1 answer:
Given :
A 12,500 kg railroad freight car travels on a level track at a speed of 5.2 m/s.
It collides and couples with a 22,600 kg second car, initially at rest and with brakes released.
To Find :
The speed of the two cars after collision.
Solution :
It is given that car couples with each other. So speed of both the cars after collision is same. Let, it be v.
Applying conservation of momentum, we get :
Therefore, the speed of the two cars after collision is 1.85 m/s.
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Complete Question:
Metal sphere A has a charge of − Q . −Q. An identical metal sphere B has a charge of + 2 Q . +2Q. The magnitude of the electric force on sphere B due to sphere A is F . F. The magnitude of the electric force on sphere A due to sphere B must be:
A. 2F
B. F/4
C. F/2
D. F
E. 4F
Answer:
D.
Explanation:
If both spheres can be treated as point charges, they must obey the Coulomb's law, that can be written as follows (in magnitude):
As it can be seen, this force is proportional to the product of the charges, so it must be the same for both charges.
As this force obeys also the Newton's 3rd Law, we conclude that the magnitude of the electric force on sphere A due to sphere B, must be equal to the the magnitude of the force on the sphere B due to the sphere A, i.e., just F.